Abstract
Using a whole-plant chamber and 203Hg-labeled mercury, a quantitative study was made of the effect of environmental parameters on the uptake, by wheat (Triticum aestivum), of metallic mercury vapor, an atmospheric pollutant. Factors were examined in relation to their influence on components of the gas-assimilation model, [Formula: see text]
where U(Hg) is the rate of mercury uptake per unit leaf surface, Ca′ is the ambient mercury vapor concentration, Cl′ is the mercury concentration at immobilization sites within the plant (assumed to be zero), rl.Hg is the total leaf resistance to mercury vapor exchange, and rm.hg is a residual term to account for unexplained physical and biochemical resistances to mercury vapor uptake.
Essentially all mercury vapor uptake was confined to the leaves. rl.hg was particularly influenced by illumination (0 to 12.8 klux), but unaffected by ambient temperature (17 to 33 C) and mercury vapor concentration (0 to 40 μg m−3). The principal limitation to mercury vapor uptake was rm.hg, which was linearly related to leaf temperature, but unaffected by mercury vapor concentration and illumination, except for apparent high values in darkness.
Knowing Ca′ and estimating rl.hg and rm.hg from experimental data, mercury vapor uptake by wheat in light was accurately predicted for several durations of exposure using the above model.
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Selected References
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